[Boatanchors] SSB Generation - Phasing VS Filter Opinion Sought

[Robert Nickels]

On 7/18/2019 10:03 PM, Whitebear1122 wrote:
> Has anyone on here built their own SSB transmitter in the past?

Hi Scott,

To me that's a question of elegance vs. brute force ;-)   Phasing is the 
way to go, IMHO.   Wes Schum and Joe Batchelor at Central Electronics 
were far ahead of the pack technically, but it really wasn't until the 
SDR became possible that the amateur world realized it.

To be fair if I was in the business of building SSB gear, especially a 
transceiver, in the 1960s the filter method was clearly the way to 
go.    But having built the W2EWL "Cheap and Easy" ssb transmitter and 
being a fan of minimalist design,  I'd vote for the phasing method for a 
one-off homebrew transmitter both as a learning experience and as a way 
to acknowledge the work of these pioneers.   Instead of just lopping off 
the unwanted sideband you would be elegantly preventing it from being 
created through the magic of phasing ;-)   (A possible side-benefit of a 
phasing rig is that they make very good-sounding AM as well).

The question is - how many bands do you want to cover?   If the answer 
is 80 and 20 meters then the "9 plus or minus 5" approach first laid out 
by Don Norgaard in 1950 provides the roadmap.   CE and others built on 
this by modifying the BC-458 VFO to provide injection for other bands, 
but that adds complexity in bandswitching or the use of plug-in coils.   
The generation of SSB on the operating frequency as was done in various 
SSB adapters including the Heathkit SB-10 and B&W offers a way around 
that and reduces the rest of the transmitter to that of a CW rig, but at 
the cost of requiring a separate RF phase shift network for each band 
(which if you borrow from their design is pretty simple).  You could 
also develop the SSB signal by phasing at a low IF of your choice (such 
as Hallicrafters did at 50 kHz) and then mixing up as in any heterodyne 
type transmitter.   As far as carrier suppression goes, it's a thing of 
beauty to hear the deep null as you adjust the balanced modulator, a 
nice feature would be to use multi-turn pots so you can really fine-tune 
it into the noise floor.

But my experience and recommendations pale in contrast with that of my 
friend Mike KG7TR, who is a master homebrewer and whose creations 
include both phasing and filter designs. http://www.kg7tr.com/

An interesting feature of his Vintage SSB Special is the use of an audio 
phase shift network made from modern components, although finding a B&W 
2Q4 - 350 network should not be difficult.   I'd urge you to have a good 
look at Mike's designs and excellent documentation for both approaches 
and see what makes the most sense to you.   Good luck on your project!

73, Bob W9RAN